This.
And this.
The mother of the bride NEVER hosts the shower. It's considered a gift grab.
But, then, I've never heard of "paying for my plate" wedding gifts either until I read about it here on the DIS.
All these "this is the way weddings & showers are done in the northeast" traditions just seem tacky & so greedy to me & are yet another reason why I'm glad I don't live there.
When we got married, I had 5 showers - a shower hosted by ladies at my church, a shower hosted by ladies at my inlaws' church, a work shower, a family shower hosted by 2 aunts, & shower hosted by a friend. Neither my mother nor I were involved in the planning or financing of any of them, & the guests (except for mother, my mother-in-law, & sister) were different at each shower.
In most instances, if you're invited to a shower, you're invited to the wedding - exceptions might be for very small family-only weddings or some kind of destination wedding where friends still want to get together a shower or some other kind of celebratory party.
However, I've never heard that every woman invited to the wedding is invited to the shower. That seems really over the top & very gift-grabby. Because, then aren't these same brides who are having these over-the-top showers also expecting a "pay for the plate" monetary gift at the wedding?
NOTE - We did have a bridesmaid brunch at a tearoom which my mother hosted - I gave gifts to my bridesmaids & maid of honor during this occasion & didn't receive any gifts myself.
If whoever is hosting the shower can't afford to host 75-100 ladies at a sit-down restaurant, then the size of the shower needs to be scaled down. And $500 should be plenty of money for a nice shower.
And, beyond possibly consulting on the guest list, the bride shouldn't be involved in the planning at all.
However, OP, since you're not contributing to the cost of the wedding, you might offer the $500 to the maid of honor or even to your DD to go toward the cost of the wedding.